#include <fstream>
#include <algorithm>
using namespace std;

int n,gr,w[5001],p[5001],i,v[2][10000001],j,k,s;
int main()
{
    ifstream f("energii.in");
    ofstream g("energii.out");

    f>>n>>gr;
    s=0;
    for (i=0;i<n;i++)
        {
            f>>w[i]>>p[i];
            s=s+w[i];
        }
    if (s>=gr)
    {
    k=1;
    for (i=0;i<n;i++)
        {
            k=1-k;
            for (j=1;j<=gr;j++)
                {
                    v[1-k][j]=v[k][j];
                    if (j<=w[i])
                                {
                                    if (v[k][j]!=0)
                                        {
                                            v[1-k][j]=min(v[k][j],v[k][w[i]-j]+p[i]);
                                        }
                                        else
                                        {
                                            v[1-k][j]=v[k][w[i]-j]+p[i];
                                        }
                                }
                                else
                                {
                                    if (v[k][j-w[i]]!=0)
                                        {
                                            v[1-k][j]=v[k][j-w[i]]+p[i];
                                        }
                                }

                }
        }
    g<<v[1-k][gr];
    }
    else
    {
    g<<"-1";
    }
    f.close();
    g.close();
    return 0;
}